Field of the invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus for acknowledgement/not-acknowledgement (ACK/NACK) transmission indicating a reception acknowledgement in a wireless communication system supporting a carrier aggregation.
Related Art
One of the most important requirements of a next generation wireless communication system is to support a high data rate. For this, various techniques such as multiple input multiple output (MIMO), cooperative multiple point transmission (CoMP), relay, etc., have been under research, but the most fundamental and reliable solution is to increase a bandwidth.
However, a frequency resource is in a saturation state at present, and various schemes are partially used in a wide frequency band. For this reason, in order to ensure a broadband bandwidth to satisfy a required higher data rate, a system is designed such that a basic requirement which allows separate bands to operate respective independent systems is satisfied, and a carrier aggregation (CA) is introduced. In concept, the CA aggregates a plurality of bands into one system. In this case, a band that can be independently managed is defined as a component carrier (CC).
The latest communication standard (e.g., 3GPP LTE-A or 802.16m) considers to expand its bandwidth to 20 MHz or higher. In this case, a wideband is supported by aggregating one or more CCs. For example, if one CC corresponds to a bandwidth of 5 MHz, four carriers are aggregated to support a bandwidth of up to 20 MHz. As such, a system supporting carrier aggregation is called a carrier aggregation system.
Meanwhile, a wireless communication system considers a system in which a base station supports a more number of user equipments in comparison with the legacy system. For example, one base station may have to support the more number of user equipments when a technique such as machine type communication (MTC), enhanced multi user multi input multi output (MIMO), etc., is applied.
In this case, it may be difficult to transmit control information to a plurality of user equipments when using only a radio resource region conventionally used to transmit the control information. In order to solve such a problem, it is considered to allocate a new control region to the radio resource region in which data is transmitted in the legacy system.
However, if scheduling information for data transmission/reception is transmitted through a new control region in a carrier aggregation system, there is a need to determine a specific method by which a user equipment transmits ACK/NACK for the data.